not to be confused
with what causes global
fluctuations in climate (not
to be confused with the recent global
warming) that the Earth has always experienced in its
history, are caused by complicated interactions between:
* Variations in the Earth's orbit
know that the Earth's orbits and degree of tilting vary with time. Its
orbit is elliptical, not circular, so there are time periods when we
are further away from sun and other periods when we are closer. The
degree of tilting also affects how much solar radiation we get
(particularly the higher latitudes).
Changes in solar activity
currently believe that Sun's radiation increases gradually during its
lifetime. According to that theory, it would have heated the Earth less
during its early days billions of years ago.
* Volcanic activity
eruptions release a lot of dust and poisonous gases such as sulphur
dioxide into the atmosphere. The particles are tiny and fly too high up
to be removed by rainfall in a hurry. They may stay up in the higher
levels of the atmosphere for a long time and they stop solar radiation
reach the Earth and consequently cause cooler temperatures. This,
however, is a relatively short-time change - it doesn't usually last
for longer than a few years max.
ages in the Earth's history coincide with major mountain building. The
high-altitude ice building in the cool temperatures higher (5,000m)
altitudes is believed to trigger a series of factors that ultimately
add to global cooling.
* Continental plate movements
of tectonic plates affect the Earth's climate not only because it
changes the position of continents and their climate, but also, and
more importantly, because it changes the shape of oceans. Oceans store
much more heat than (the air above) continents. Also, ocean currents
are the main heat transferers between different latitudes. Without Golf
Stream for example, Scandinavia would be uninhabitable, and the current
global warming threatens to turn off the Gulf Stream some time in the
* Greenhouse gases
gases such as carbon dioxide, methane and water vapour trap the heat in
the atmosphere and higher concentrations of those gases match warmer
periods in the Earth's history.
cannot do anything about solar activity, the Earth's orbit, continental
drift, volcanism or mountain building. Solar activity, the Earth's
orbit, mountain building and continental drift add to very long term
changes anyway, much longer than a few hundred years. Volcanism can
cause short term changes but it has cooling,
warming effects. So if looking for not only what causes climate change
but causes for the current short-term
are left with greenhouse gases. They are by far the biggest
factor behind it. And,
they are the only
point on the list above that we can
do something about.
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does that mean?